On 3 July 1782, Frances gave birth to a child. During their estrangement, Frances lived under a different name, Langley, in order to hide her location from her husband, although he still learned of her whereabouts. On 23 July 1781, when Matthew was six and his youngest sister one-and-a-half years old, Frances left her husband, taking the music master, Samuel Harrison, as her lover.

In addition to Matthew Gregory Lewis, Matthew and Frances had three other children: Maria, Barrington, and Sophia Elizabeth. His son would later inherit this property. Lewis owned considerable property in Jamaica, within four miles of Savanna-la-Mer, or Savanna-la-Mar, which was hit by a devastating earthquake and hurricane in 1779. With one exception, he was the first to hold both positions and receive both salaries contemporaneously. In December 1775, in addition to his War Office post, Lewis became the Deputy Secretary at War. As a child, she spent her time in Ottershaw. Her family, like Lewis's, had connections with Jamaica. She was the third daughter of the senior judge Sir Thomas Sewell and was one of eight children born in his first marriage to Catherine Heath. The following year, he married Frances Maria Sewell, a young woman who was very popular at court. That same year, Lewis was appointed Chief Clerk in the War Office. The correspondence between Matthew and his mother consisted of discussion regarding the poor state of his mother's welfare and estate. Mrs Lewis moved to France in this period while there, she was in continuous correspondence with Matthew. During his time at Westminster, Lewis's parents separated, and he idolised his mother without disregarding his father. He attended Westminster School before proceeding to Christ Church, Oxford, where he received his bachelor's degree in 1769 and his master's in 1772. His father, Matthew Lewis, was the son of William Lewis and Jane Gregory and was born in England in 1750. Lewis was the first-born child of Matthew and Frances Maria Sewell Lewis. He also worked as a diplomat, politician and an estate owner in Jamaica. He was frequently referred to as ' Monk' Lewis, because of the success of his 1796 Gothic novel The Monk. Matthew Gregory Lewis (9 July 1775 – 14 or ) was an English novelist and dramatist, whose writings are often classified as 'Gothic horror'.

The monk gregory lewis